Methods for manufacturing curable inks for digital offset printing applications and the inks made therefrom

Abstract

Methods for making pigmented, curable, liquid ink compositions, and the ink compositions prepared from the methods are disclosed. The method includes adding at least one monomer and a dispersant to mixing vessel, and metering into the mixing vessel at least one pigment over a period of time. The method further includes adding at least one initiator and at least one curing agent, and then milling the composition. The pigmented, curable, high viscosity liquid ink compositions are suitable for digital offset printing.

What is claimed is: 
     
       1. A method for preparing a pigmented, curable, digital lithographic ink composition, comprising:
 a) adding to a mixing vessel at least one monomer or oligomer and at least one dispersant; 
 b) heating the mixing vessel; 
 c) adding at least one initiator and a thermal stabilizer, and optionally a leveling agent, while mixing; 
 d) adding at least one pigment, and optionally an inorganic filler, while stirring to form a pigmented radiation curable ink composition; 
 e) cooling the pigmented radiation curable ink composition to about room temperature; and 
 f) milling the pigmented radiation curable ink composition to reduce the particle size of the pigmented, curable ink composition to less than about 1 μm to prepare a pigmented, curable, ink composition. 
 
     
     
       2. The method of  claim 1 , wherein at least one pigment is added over a period of from about 10 minutes to about 30 minutes for a 400 g scaled batch process. 
     
     
       3. The method of  claim 1 , wherein a clay is added with at least one pigment, after addition of pigments. 
     
     
       4. The method of  claim 1 , wherein milling the pigmented radiation curable ink composition in f) comprises adding the composition to a 3-roll milling apparatus. 
     
     
       5. The method of  claim 1 , wherein the mixing vessel is heated in (b) to a temperature of from about 40° C. to about 95° C. 
     
     
       6. The method of  claim 5 , wherein the mixing vessel is heated to a temperature of from about 65° C. to about 80° C. 
     
     
       7. The method of  claim 1 , further comprising mixing the homogenous mixture after c) adding at least an initiator and a thermal stabilizer, and optionally a leveling agent, and before d) adding the at least one pigment for a period of time of from about 5 minutes to about 80 minutes. 
     
     
       8. The method of  claim 7 , wherein the mixture is mixed in c) for a period of time of from about 30 minutes to about 45 minutes. 
     
     
       9. A method for preparing a pigmented, curable, ink composition comprising:
 a) adding to mixing vessel at least one monomer and at least one dispersant; 
 b) heating the mixing vessel to a temperature within the range of from about 40° C. to about 95° C.; 
 c) adding at least one pigment while stirring to form a homogenous mixture; 
 d) further mixing the homogenous mixture for a period of from about 5 minutes to about 80 minutes; 
 e) adding to the homogenous mixture at least an initiator and a thermal stabilizer, and optionally a leveling agent, while mixing to form a pigmented radiation curable ink composition; 
 f) cooling the pigmented radiation curable ink composition to about room temperature; 
 g) milling the pigmented radiation curable ink composition to reduce the particle size of the pigmented, curable ink composition to less than about 1 μm to prepare a pigmented, curable, ink composition; 
 h) optionally returning the contents to a mixing vessel after milling, heating and mixing the ink composition, and adding at least one monomer to the vessel while stirring to form homogenous ink composition mixture; and 
 i) milling the homogenous ink composition mixture to prepare a finished pigmented, curable, liquid ink composition. 
 
     
     
       10. The method of  claim 9 , wherein the at least one pigment is added in c) over a period of from about 10 minutes to about 30 minutes. 
     
     
       11. The method of  claim 9 , wherein a clay is added together with the at least one pigment in c). 
     
     
       12. The method of  claim 9 , wherein the homogenous mixture is mixed in d) for a period of time of from about 30 minutes to about 40 minutes. 
     
     
       13. The method of  claim 9 , wherein milling the pigmented radiation curable ink composition in g) comprises charging the composition to a 3-roll milling apparatus for at least 2 passes and i) comprises charging the composition to a 3-roll milling apparatus once. 
     
     
       14. The method of  claim 9 , wherein the mixing vessel is heated in b) and h) to a temperature of from about 55° C. to about 85° C. 
     
     
       15. The method of  claim 14 , wherein the mixing vessel is heated in b) and h) to a temperature of from about 65° C. to about 80° C.